The world reference center for arboviruses identifies and characterizes any virus suspected of being biologically transmitted by arthropods. A collection of 379 already characterized reference viruses and sera is utilized in the neutralization, complement-fixation, and hemagglutination-inhibition tests to determine the relationship of referred viruses to the reference viruses. Physical and morphologic characteristics of selected new arboviruses are determined using electron microscopy and polyacrylamide gel electrophoresis. The collection is also used for serological diagnosis of disease, study of epidemics, and survey for antibody. This collection of reference arboviruses is the only relatively complete collection existing in the world. The long-term aim is to develop new research areas and research models in virology and epidemiology such as has been done in the past with rabies-related viruses, the Colorado tick fever-Eyach group of orbiviruses, mosquito tissue culture, and tick-borne orbiviruses from Ixodes uriae.